1. The Field of the Invention
The present invention relates generally to devices to replace knots and more specifically to devices to replace surgical knots tied in open, arthroscopic, and endoscopic procedures.
2. The Relevant Technology
Numerous devices have been developed to eliminate the need to tie knots as a way of securing a line. The devices that accomplish the same function as a knot, which is in part to secure a line to retain tension in a portion of the line, are typically referred to as line locks.
Line locks generally operate in one of two ways. Some line locks are manually actuated to secure one or more lines so that tension is maintained in a portion of the line(s). Once actuated, the line lock resists sliding along the line(s) either toward or away from the tensioned portion of the line. Other line locks are continuously adjustable in one direction so that tension is increased in the portion of the line upon which the line lock is advanced. The continuously adjustable line locks resist movement away from the tensioned portion of the line, but can be further advanced toward the tensioned portion of the line with an appropriately applied force.
The portion of a line that is put under tension, typically to secure some object, is commonly referred to as the standing end. The portion of the line that extends toward the line handler is commonly referred to as the working end. A knot in a line, or a line lock attached to a line, is the demarcation between the standing end and the working end.
Continuously adjustable line locks offer several advantages. They are passive locking devices, meaning that no other operation is required to secure the line lock once it is moved along the line to its desired position. Furthermore, these line locks can be used to continuously increase the tension in the standing end until it reaches a desired level of tension.
The advantages of line locks over tied knots are very attractive in many varied applications, including the use of surgical sutures. However, the line locks developed to date have many deficiencies when considered for surgical suture applications. For example, known line locks use line on line friction to create the locking effect, and this line on line friction makes it difficult to advance the line lock over suture. Known line locks rely on maintenance of tension in the standing end to prevent the line lock from migrating back along the working end.
In surgical suture applications, the working end is typically trimmed closely to the line lock. As a result, the line lock can easily disassociate from the suture once tension in the standing end is lost. In most, if not all, surgical applications, a free-floating device such as a line lock can potentially harm adjacent body tissues. Additionally, known line locks are susceptible to loosening during cyclic variations in the tension of the standing end. This cyclic variation in the standing end tension is common in surgical applications as tissues are stressed and then relaxed. Loosening of the line lock thus compromises the securing function for which it was intended. Furthermore, known line locks are often somewhat bulky, and are therefore not optimally designed for implantation in the body.